[ELI5] Why do smaller rechargeable batteries (smartphones, power banks) use mAh to measure capacity, while larger batteries (laptops, EVs) use kWh?

Question

How come some use Watt-Hours and some use Ampere-Hours?

In: Technology

Answer 1

It depends on the power.

If you recorded a small battery in kWh then you might be advertising a battery as being 0.01kWh – which is the same as 1000mWh but sounds small in comparison.

If you had a 1kWh battery and expressed it as 1000000mWh which people would not necessarily believe the claim since it looks like an outrageous power.

With few exceptions (for example in precision engineering) you would not say that something that is 10 meters long was 10,000,000mm long, or even 10,000 cm.